Lesson 1 · from §77 of the 1910 text
Reading a Graph: The Temperature Curve
A graph
A graph is a picture of how one quantity changes with another. The curve below was made by a recording thermometer. An arm carrying a pen moves up as the temperature rises and down as it falls, while a clock movement runs a strip of cross-ruled paper under the pen. The result is a continuous line. This record runs from 2 P.M. Wednesday to 10.30 A.M. the Friday following (redrawn here from the book's record of February 1908).
The numbers 40 to 90 at the left are degrees Fahrenheit; each small space is 2 degrees. The numbers along the bottom give the hour of the day.
- Point A tells us that at 2 P.M. Wednesday the temperature was 80 degrees.
- Point B, at 7 P.M. Wednesday, marks the highest temperature recorded.
- Point C tells us the temperature was about 65\frac12 degrees at 6 A.M. Thursday.
The record was made indoors. The sudden fall from D to E came when a door to a cold hallway was opened: the temperature of the room fell about 18 degrees in about 30 minutes.
To read a graph, go across to find a time, then up to the curve, then left to read the temperature. To find when a temperature occurred, go the other way: across from the temperature to the curve, then down to the time.
A graph like this has practical uses: it can show whether a building is being overheated when no one is in it (a waste of coal), or how evenly a room or a railroad car is being kept warm.
Try one:
Quick check
From the temperature graph, what was the temperature at point D, just before the door was opened?
Exercises
How to type math
Use ^ for powers (a^2), / for fractions ((a+b)/2), sqrt(x) for square roots, and cbrt(x) for cube roots. You can leave out the multiplication sign: 3ab means 3 \cdot a \cdot b. Mixed numbers like 4 1/2 work too. The preview under each box shows how your answer was read.
Use the temperature graph above. Give numbers only; the units are filled in.
With what temperature does the record begin? end?
What is the highest temperature recorded? the lowest?
About what time was the highest temperature recorded? the lowest?
How often did the instrument record a temperature of 80 degrees? 72 degrees? 78 degrees? 62 degrees?
At what times did it record a temperature of 80 degrees? Give the times on Thursday and Friday.
The fall from D to E happened when a door to a cold hallway was opened. About how many degrees did the temperature fall, and in about how many minutes?